Thermoelectric transducer and thermoelectric transducer module

ABSTRACT

A thermoelectric transducer includes a substrate, a thermoelectric film on the substrate, a first electrode on the substrate, and a second electrode on the substrate, the second electrode being different from the first electrode in work function. The first electrode and the second electrode are in contact with the same side of the thermoelectric film. The outer edge of the thermoelectric film is located inner than the outer edge of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2020-102495 filed in Japan on Jun. 12,2020, the entire content of which is hereby incorporated by reference.

BACKGROUND

This disclosure relates to a thermoelectric transducer and athermoelectric transducer module.

The commonly used thermoelectric generator that utilizes waste heat is abismuth-telluride (Bi₂Te₃)-based Peltier device. JP 2016-219609 Adiscloses a different type of thermoelectric transducer including athermoelectric film (semiconductor film) such as an Al-doped zinc oxide(ZnO) film or an Ag-doped magnesium silicide (Mg₂Si) film with metalelectrodes having different work functions thereon, and a powergeneration device including the thermoelectric transducer. For example,when a first electrode and a second electrode are connected with athermoelectric film of an n-type semiconductor, electrons tend to flowin the electrode having a lower work function, rather than the electrodehaving a higher work function. As a result, thermal electromotive forceis generated between the electrodes.

SUMMARY

An aspect of this disclosure is a thermoelectric transducer including: asubstrate; a thermoelectric film on the substrate; a first electrode onthe substrate; and a second electrode on the substrate, the secondelectrode being different from the first electrode in work function. Thefirst electrode and the second electrode are in contact with the sameside of the thermoelectric film. The outer edge of the thermoelectricfilm is located inner than the outer edge of the substrate.

Another aspect of this disclosure is a thermoelectric transducerincluding: a substrate; a thermoelectric film on the substrate; a firstelectrode on the substrate; and a second electrode on the substrate, thesecond electrode being different from the first electrode in workfunction. The first electrode and the second electrode are in contactwith the same side of the thermoelectric film. The first electrodeincludes a first connection terminal part. The second electrode includesa second connection terminal part. The first connection terminal partand the second connection terminal part are distant from thethermoelectric film when viewed planarly.

Another aspect of this disclosure is a thermoelectric transducer moduleincluding: a substrate; a thermoelectric film on the substrate; a firstelectrode on the substrate; a second electrode on the substrate, thesecond electrode being different from the first electrode in workfunction; a first lead wire interconnected with a connection terminalpart of the first electrode; and a second lead wire interconnected witha connection terminal part of the second electrode. The first electrodeand the second electrode are in contact with the same side of thethermoelectric film. A joint between the connection terminal part of thefirst electrode and the first lead wire, the first lead wire, a jointbetween the connection terminal part of the second electrode and thesecond lead wire, and the second lead wire are distant from thethermoelectric film when viewed planarly.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan diagram of a configuration example of thethermoelectric transducer module in Embodiment 1;

FIG. 2 illustrates a first electrode extracted from the thermoelectrictransducer illustrated in FIG. 1;

FIG. 3 schematically illustrates the ideal connection of the conductivecomponents in a thermoelectric transducer;

FIG. 4 schematically illustrates a state where parasitic devices aregenerated;

FIG. 5A is a plan diagram of a thermoelectric transducer;

FIG. 5B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 5A;

FIG. 5C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 5A;

FIG. 6 illustrates a configuration example of the joint between a leadwire and a connection terminal part;

FIG. 7 illustrates another configuration example of the joint between alead wire and a connection terminal part;

FIG. 8 schematically illustrates a cross-section of anotherconfiguration example of the thermoelectric transducer;

FIG. 9 schematically illustrates thermoelectric transducers before beingcut out from a mother substrate;

FIG. 10A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 10B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 10A;

FIG. 11A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 11B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 11A;

FIG. 12A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 12B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 12A;

FIG. 12C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 12A;

FIG. 13A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 13B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 13A;

FIG. 13C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 13A;

FIG. 14A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 14B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 14A;

FIG. 14C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 14A;

FIG. 15 is a plan diagram of a configuration example of thethermoelectric transducer in Embodiment 2;

FIG. 16 is a cross-sectional diagram along the section line XVI-XVI inFIG. 15;

FIG. 17A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 17B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 17A;

FIG. 18A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 18B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 18A;

FIG. 18C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 18A;

FIG. 19A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 19B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 19A;

FIG. 19C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 19A;

FIG. 20A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 20B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 20A;

FIG. 20C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 20A;

FIG. 21 is a plan diagram of a configuration example of thethermoelectric transducer in Embodiment 3;

FIG. 22 is a plan diagram of a configuration example of thethermoelectric transducer in Embodiment 4;

FIG. 23A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 23B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 23A;

FIG. 24A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 24B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 24A;

FIG. 25A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 25B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 25A;

FIG. 26A is a plan diagram of a configuration example of athermoelectric transducer in Embodiment 5;

FIG. 26B is a cross-sectional diagram of the thermoelectric transducerin FIG. 25A along the section line B-B;

FIG. 26C is a cross-sectional diagram of the thermoelectric transducerin FIG. 25A along the section line C-C;

FIG. 27A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 27B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 27A;

FIG. 28A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 28B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 28A;

FIG. 29A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 29B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 29A;

FIG. 29C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 29A;

FIG. 30A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 30B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 30A;

FIG. 30C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 30A;

FIG. 31A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 31B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 31A;

FIG. 31C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 31A;

FIG. 32 illustrates a configuration example of a joint;

FIG. 33 illustrates another configuration example of a joint;

FIG. 34A is a plan diagram of a configuration example of thethermoelectric transducer in Embodiment 6;

FIG. 34B is a cross-sectional diagram of the thermoelectric transducerin FIG. 34A along the section line B-B;

FIG. 34C is a cross-sectional diagram of the thermoelectric transducerin FIG. 34A along the section line C-C;

FIG. 35A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 35B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 35A;

FIG. 36A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 36B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 36A;

FIG. 36C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 36A;

FIG. 37A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 37B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 37A;

FIG. 37C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 37A;

FIG. 38A is a plan diagram of a structure in manufacturing athermoelectric transducer;

FIG. 38B schematically illustrates the cross-sectional structure alongthe section line B-B in FIG. 38A;

FIG. 38C schematically illustrates the cross-sectional structure alongthe section line C-C in FIG. 38A; and

FIG. 39 is a plan diagram of a configuration example of a thermoelectrictransducer in Embodiment 7.

EMBODIMENTS

Hereinafter, embodiments will be described specifically with referenceto the accompanying drawings. Elements in the drawings may beexaggerated in size and/or shape for clear understanding of thedescription. Described hereinafter is a thermoelectric transducer thatcan be used as a sensing device for sensing heat from an object or apower generation device for generating electricity with heat from a heatsource. The thermoelectric transducer includes a thermoelectric film, afirst electrode, and a second electrode fabricated on a substrate. Thefirst and the second electrodes are laid on the thermoelectric film; thefirst and the second electrodes are in contact with one side of thethermoelectric film. The thermoelectric transducer can include three ormore electrodes.

When temperature difference occurs across the thickness of thethermoelectric film, charge density gradient arises in accordance withthe temperature gradient. When the first electrode and the secondelectrode having different work functions are in contact with the sameside of the thermoelectric film, charges move in or move out betweeneach electrode and the thermoelectric film. The mobility of the chargesdepends on the work function. Accordingly, thermal electromotive forceis generated between the two electrodes in response to not onlytemperature difference occurring in the plane of the thermoelectric filmbut also temperature difference occurring across the thickness of thethermoelectric film. The difference in thermal electromotive forcebetween the first electrode and the second electrode is taken out as theoutput of the thermoelectric transducer. To prevent effect of aparasitic device on the output, the thermoelectric element has astructure for preventing generation of the parasitic device.

In an example in this description, the outer edge of the thermoelectricfilm that contributes to the thermal electromotive force to be output islocated inner than the outer edge of the substrate. In other words, theoutline of the thermoelectric film is located inner than the outer edgeof the principal surface of the substrate when viewed planarly. Thisconfiguration prevents generation of a parasitic device because ofcontact of the thermoelectric film with a conductor such as a heatsource or an object to be measured.

In an example of this description, the joint between the first electrodeand an external lead wire and the joint between the second electrode andan external lead wire are located outside and distant from thethermoelectric film that contributes to generation of thermalelectromotive force. The joints are made of solder or conductiveadhesive. The external lead wires are also distant from thethermoelectric film. The joints and the lead wires are not in directcontact with but are distant from the thermoelectric film to avoidgeneration of parasitic devices at the joints.

In an example of this description, each of the first electrode and thesecond electrode is one electrode film and includes an electromotivepart that is laid on the thermoelectric film and contributes togeneration of thermal electromotive force and a connection terminal partfor taking out the output to the external. In an example, the connectionterminal part is disposed outside the region of the thermoelectric filmthat contributes to generation of thermal electromotive force. Thisconfiguration prevents a lead wire connected with the connectionterminal part from contacting the thermoelectric film without beingmediated by the connection terminal part and accordingly avoidsgeneration of a parasitic device. The connection terminal part can belaid on a film that is made of the same material as the thermoelectricfilm that contributes to generation of thermal electromotive force anddisposed outside the region of the thermoelectric film.

Embodiment 1

FIG. 1 is a plan diagram of a configuration example of a thermoelectrictransducer module in an embodiment of this description. Thethermoelectric transducer module includes a thermoelectric transducer 15and external lead wires (also simply referred to as lead wires) 141 and142 for transmitting the thermal electromotive force generated in thethermoelectric transducer 15. The lead wires 141 and 142 areinterconnected with electrodes of the thermoelectric transducer 15 bysolder joints 121 and 122. The thermoelectric transducer module isapplicable to a sensing device for sensing heat of an object to bemeasured or a power generation device that generates electricity withheat from a heat source.

The thermoelectric transducer 15 includes a thermoelectric film 103, afirst electrode 111, and a second electrode 112 fabricated on asubstrate 100. The thermoelectric transducer 15 can include three ormore electrodes. In the configuration example in FIG. 1, the substrate100 is a flexible substrate made of an organic material such aspolyimide. The flexible substrate 100 is made thin (for example 10 μm to100 μm) for low thermal resistance.

The thermoelectric film 103 can be made of a desirable material thatgenerates a carrier density gradient when a temperature gradient iscreated in the film. The carriers move to cancel this gradient, so thatelectromotive force is generated between the electrodes 111 and 112. Inthe configuration example in FIG. 1, the thermoelectric film 103 is madeof a semiconductor material such as In—Ga—Zn—O (IGZO), aluminum-dopedZnO, or silver-doped Mg₂Si.

The first electrode 111 and the second electrode 112 are disposed to beseparate from each other on the substrate 100. A part of the firstelectrode 111 and a part of the second electrode 112 are laid on thethermoelectric film 103. These parts of the first electrode 111 and thesecond electrode 112 are in contact with the same principal surface ofthe thermoelectric film 103 and the remaining parts are in contact witha principal surface of the substrate 100. The layered area where theelectrode 111 or 112 is laid on the thermoelectric film 103 correspondsto the thermal electromotive part for generating electromotive force inaccordance with the external heat.

The first electrode 111 and the second electrode 112 have different workfunctions. The material having a smaller work function can be Cs, Al, orTi and the material having a larger work function can be Ni or Cu. Anymaterials can be selected desirably as far as their work functions aredifferent.

The electrode having a smaller work function exhibits higher ohmiccharacteristic than the electrode having a larger work function whenthey are in contact with an n-type thermoelectric film. For this reason,more electrons flow from the thermoelectric film 103 into the electrodehaving the smaller work function. In the case of an p-typethermoelectric film, more holes flow from the thermoelectric film 103into the electrode having the larger work function. Accordingly, whentemperature gradient is present along the normal to the thermoelectricfilm 103 (in the direction of thickness or layering), the chargepotentials at the first electrode 111 and the second electrode 112become different to generate thermal electromotive force.

Each of the lead wires 141 and 142 includes a conductor for transmittinga signal and a covering surrounding the conductor. The exposed parts ofthe conductors of the lead wires 141 and 142 are disposed not to overlapthe thermoelectric film 103 when viewed planarly. However, if thethermoelectric film 103 is covered with an insulative protection film,these exposed parts can overlap the thermoelectric film 103 when viewedplanarly.

FIG. 2 illustrates the first electrode 111 extracted from thethermoelectric transducer 15 in FIG. 1. The first electrode 111 is asingle metallic thin film and has a plurality of parts. The partsurrounded by a broken line 201 is an electromotive part, which is incontact with the thermoelectric film 103 and included in the thermalelectromotive part.

The part surrounded by a broken line 203 is a lead part connecting theconnection terminal part 131 and the electromotive part. It is locatedoutside the region of the thermoelectric film 103 and is in contact withthe substrate 100. The lead part 203 is optional. Although theconnection terminal parts 131 and 132 in the configuration exampleillustrated in FIGS. 1 and 2 have a rectangular shape wider than thelead parts, the shape of the connection terminal parts 131 and 132 isnot limited to a specific one.

The configuration such that the connection terminal part 131 forconnecting the module to the external and the electromotive part 201 forconverting heat to electricity are included in one metallic thin filmdoes not significantly affect the manufacturing process and is effectiveto take out the output voltage. The second electrode 112 is also asingle metallic thin film; it has an electromotive part laid on thethermoelectric film 103 to be included in the thermal electromotivepart, and a lead part and a connection terminal part 132 located outsidethe region of the thermoelectric film 103.

The electromotive parts of the first electrode 111 and the secondelectrode 112 in the configuration example in FIGS. 1 and 2 havecomb-like shapes. Their teeth are disposed to engage with each other.That is to say, the teeth of the first electrode 111 are disposed to bealternate with the teeth of the second electrode 112 in the verticaldirection in FIG. 1 so that each tooth of one electrode is opposed to atooth of the other electrode within a plane. This configuration enablesefficient output of thermal electromotive force. The shapes of theelectrodes 111 and 112 in FIGS. 1 and 2 are merely an example; theelectrodes can have different shapes.

One of the requirements for the thermoelectric transducer 15 is toefficiently transmit external heat or variation in temperature to thethermal electromotive part where the thermoelectric film 103 and theelectromotive parts are layered. In the case of using the thermoelectrictransducer 15 as a sensing device, this is an important condition toattain high responsiveness. However, the main body composed of thinfilms of the thermoelectric film 103 and the electrodes 111 and 112 isdifficult to maintain its structure by itself; a structure such that themain body is supported by an insulative substrate is effective.

Supposing that the thermoelectric transducer 15 is used in a state wherean object is put against the rear surface of the substrate 100, which isthe opposite surface of the surface on which the thermoelectric film 103is provided, the substrate 100 becomes resistive to transmission ofheat. Accordingly, reducing the thermal influence by reducing thethermal resistance of the substrate 100 is an approach to efficienttransmission of heat to the thermal electromotive part.

It is effective to employ a material having high thermal conductivityfor the substrate 100 or to make the substrate 100 thin. However, a thindevice including a substrate 100 of a brittle material such as glass hasa high possibility of breakage. A substrate made of a polyimide filmhaving a thickness of approximately 10 μm to 100 μm makes thethermoelectric transducer 15 flexible and allows attachment to a curvedsurface. The thermoelectric transducer 15 is supposed to be used in ahigh-temperature place and therefore, polyimide is a favorable material.However, the material can be selected from other various substances suchas polyethylene terephthalate (PET) resin, liquid polymer (LCP),silicone resin, and epoxy resin in view of the conditions such as thetemperature range in the operating environment, the manufacturingmethod, and the cost.

As illustrates in FIG. 1, the thermoelectric transducer 15 is fabricatedso that the outer edge (outline) of the thermoelectric film 103 forcontributing to the device operation such as sensing or generatingelectricity is located inner than the outer edge of the insulativesubstrate 100. Further, the first electrode 111 includes an integrallyformed connection terminal part 131 and the second electrode 112includes an integrally formed connection terminal part 132 in order toconnect the part for contributing to the device operation to theexternal. The connection terminal parts 131 and 132 are laid neither onnor in contact with the thermoelectric film 103 for contributing to thedevice operation. This configuration prevents generation of a parasiticdevice.

Parasitic devices in the thermoelectric transducer are described. FIG. 3schematically illustrates the ideal connection of the conductivecomponents in the thermoelectric transducer 15. The solid lines betweencomponents represent contacts; the components are in direct contact witheach other. The thermoelectric transducer 15 outputs an electromotiveforce depending on the difference between the work functions of theelectrodes that are in contact with the thermoelectric film 103. Theconductors in direct contact with the thermoelectric film 103 are onlythe electrodes 111 and 112; none of the solder joints 121 and 122 andthe lead wires 141 and 142 are in contact with the thermoelectric film103. The thermoelectric film 103 is not in contact with an object suchas an object to be measured or a heat source, either.

FIG. 4 schematically illustrates a state where parasitic devices aregenerated. The solid lines between components represent ideal contactsand the broken lines represent contacts that generate a parasiticdevice. When a component other than the electrodes 111 and 112, namely asolder joint or a lead wire, is in direct contact with thethermoelectric film 103, a parasitic device is generated.

In most cases, the solder joints 121 and 122 and the lead wires 141 and142 are made of metallic materials different from the materials of theelectrodes 111 and 112. In other words, they are made of materialshaving work functions different from the work functions of the materialsof the electrodes 111 and 112. When one of these is in contact with thethermoelectric film 103 that contributes to generation of thermalelectromotive force, a potential different from the potential generatedwith the electrode 111 or 112 could be generated. This potential isgenerated in parallel to the potentials properly generated in thethermoelectric device and accordingly, its effect is superimposed on theoutput. In FIG. 4, the solder joints 121 and 122 are in contact with thethermoelectric film 103 and further, an object 25 such as an object tobe measured or a heat source is also in contact with the thermoelectricfilm 103. Parasitic devices are generated at these components.

Conditions to generate a parasitic device as described above aredescribed. First, the contact between the object 25 and thethermoelectric film 103 is described. A method of manufacturing thethermoelectric transducer 15 produces components of a plurality ofthermoelectric transducers 15 by forming electrodes on a thin polyimidefilm having a thickness of 10 μm to 20 μm by thin-film process such assputtering or vacuum vapor deposition and depositing a protection filmas necessary, and thereafter, cuts out individual thermoelectrictransducers 15.

For example, the manufacturing procedure deposits one thermoelectricfilm on the entire polyimide film, forms a plurality of pairs ofelectrodes for a plurality of thermoelectric transducers on thethermoelectric film, and covers the thermoelectric film and theelectrodes with a polyimide protection film. This protection film hasopenings to expose the terminals. Since the thermoelectric film isprovided on the entire polyimide film, the thermoelectric film issandwiched between the polyimide substrate and the protection film inthe cross-section along the outer edge of the thermoelectric transducer.The polyimide film for a substrate can be formed on a support substratesuch as a glass substrate and removed from the support substrate afterthe foregoing manufacturing procedure is finished.

Since the substrate and the protection film are both very thin (as thinas 10 μm to 20 μm), the thermoelectric film is close to the attachmentsurface of an object such as an object to be measured or a heat source.Although some methods such as machine processing with a die or a Thomsonblade and laser cutting are available to cut out the outline, thethermoelectric film could hang over because of shear droop. For thisreason, the thermoelectric film gets closer to the attachment surface atthe end of the thermoelectric transducer, increasing the possibility ofthe electrical contact between an object and the thermoelectric film.

If the object is a conductor, the object is more likely to have somepotential. Contact of the object with the thermoelectric film generatesa parasitic device, which affects the output of the thermoelectrictransducer. In general, the contact that generates a parasitic device isnot so reproducible and the contact is not stable in itself.Accordingly, a parasitic device will cause differences incharacteristics among a plurality of thermoelectric transducers orinstability of output within a thermoelectric transducer. In thestructure of this embodiment, the thermoelectric film 103 is distantfrom the outer edge of the substrate 100 and therefore, when thethermoelectric transducer 15 is attached to an object, the object isless likely to contact thermoelectric film 103.

Next, the contact between the solder joint 121 or 122 and thethermoelectric film 103 is described. In connecting a lead wire to aconnection terminal part by soldering, the solder produces a diffusionlayer with the electrode layer to be connected. The electrode layer isformed by thin-film process and is as thin as approximately dozens ofnanometers to one micrometer. Part of the solder may penetrate theelectrode layer of the connection terminal part, so that the solder (andthe lead wire) could contact the thermoelectric film 103 directly.

The operation of the thermoelectric transducer 15 is based on thebalance of the mobility of charges at the interfaces of the electrodes111 and 112 with the thermoelectric film 103. Accordingly, an unexpectedparasitic device between the thermoelectric film 103 and the solderjoint 121 or 122 or the lead wire 141 or 142 causes unexpected effect onthe output. The extent of the effect differs depending on the area ofthe solder that is in contact with the thermoelectric film through anelectrode, causing variation in characteristics.

To eliminate the effect of a parasitic device, it is effective that thethermoelectric transducer 15 has a structure not to produce a contact togenerate a parasitic device. If a conductor other than the electrodes111 and 112 may contact the thermoelectric film 103, processing byremoving a part of the thermoelectric film 103 is effective to preventthe contact.

As described above, a configuration such that the outer edge of thethermoelectric film 103 is located inner than the outer edge of thesubstrate 100 reduces the possibility that an object contacts thethermoelectric film 103 at the end of the thermoelectric transducer 15.Further, a disposition such that the connection terminal parts 131 and132 of the electrodes 111 and 112 are not in contact with but aredistant from the thermoelectric film 103 on the substrate 100effectively prevents generation of a parasitic device because of contactof the solder joint 121 or 122 or the lead wire 141 or 142 with thethermoelectric film 103.

Hereinafter, the cross-sectional structure of the thermoelectrictransducer 15 is described. FIG. 5A is a plan diagram of athermoelectric transducer 15. FIG. 5B schematically illustrates thecross-sectional structure along the section line B-B in FIG. 5A. FIG. 5Cschematically illustrates the cross-sectional structure along thesection line C-C in FIG. 5A. FIG. 5B illustrates a cross-section of apart including the connection terminal parts 131 and 132 of thethermoelectric transducer 15. FIG. 5C illustrates a cross-section of apart including the electromotive parts 201 and 202 of the electrodes 111and 112 of the thermoelectric transducer 15. The electromotive parts 201and 202 are laid on the thermoelectric film 103 and included in thethermal electromotive part.

As illustrated in FIG. 5B, the connection terminal parts 131 and 132 arein contact with one side of the substrate 100 and located outside theregion of the thermoelectric film 103 within this side of the substrate.Since the connection terminal parts 131 and 132 are distant from thethermoelectric film 103 when viewed planarly, this configurationprevents contact of the solder joint 121 or 122 or the lead wire 141 or142 to the thermoelectric film 103 to generate a parasitic device.

As illustrated in FIG. 5C, the part 201 of the first electrode 111 andthe part 202 of the second electrode 112 are laid on and in contact withthe thermoelectric film 103. Accordingly, thermal electromotive force isgenerated between the first electrode 111 and the second electrode 112.In the example in FIGS. 5B and 5C, the thermoelectric film 103 and theconnection terminal parts 131 and 132 are provided above and in contactwith the substrate 100. In another example, interlayer films of aninorganic insulator can be provided between the thermoelectric film 103and the substrate 100 and between the connection terminal parts 131 and132 and the substrate 100.

FIGS. 6 and 7 illustrate configuration examples of the joint between alead wire and a connection terminal part. Even if the solder joint 121or 122 penetrates the connection terminal part 131 or 132 as illustratedin FIG. 6, none of the solder joints 121 and 122 and the lead wires 141and 142 contact the thermoelectric film 103.

Even if soldering is dislocated from the connection terminal part asillustrated in FIG. 7, none of the solder joints 121 and 122 and thelead wires 141 and 142 contact the thermoelectric film 103. As notedfrom these examples, the structure in this embodiment preventsgeneration of an undesirable parasitic device, so that thethermoelectric transducer 15 exhibits stable characteristics.

FIG. 8 schematically illustrates a cross-section of anotherconfiguration example of the thermoelectric transducer 15. Theconfiguration example illustrated in FIG. 8 includes an insulativeprotection film 210 covering the components. The protection film 210 hasnot-shown openings and the connection terminal parts 131 and 132 areexposed through the openings. The protection film 210 can be made of aninsulative organic substance such as polyimide. The protection film 210prevents electric contact of an external object to any of the electrodes111 and 112 and the thermoelectric film 103.

Hereinafter, an example of the method of manufacturing thethermoelectric transducer 15 in Embodiment 1 is described. FIG. 9schematically illustrates thermoelectric transducers 15 before being cutout from a mother substrate 220. The dashed-dotted lines represent thecut lines to cut out the thermoelectric transducers 15. As describedabove, the thermoelectric transducers 15 are cut out from the mothersubstrate 220 by machine processing or laser cutting.

The thermoelectric transducer 15 is manufactured by thin-film process.The cost of manufacture by thin-film process can be lowered byincreasing the number of transducers to be simultaneously fabricated onone mother substrate 220 as illustrated in FIG. 9.

A method that fabricates a structure of the thermoelectric transducerfor achieving the required function by thin-film process, manufacturesthe other parts such as lead wires by an independent low-cost method,and joins them is an effective choice. This embodiment fabricates thestructure for generating thermal electromotive force and connectionterminal parts to be connected with lead wires for taking out the outputto the external by thin-film process.

An example of the manufacturing procedure forms a polyimide film on aglass substrate, deposits the other components of thermoelectrictransducers on the polyimide film, and removes the glass substrate fromthe polyimide film before or after cutting out the thermoelectrictransducers 15. In the following, such an example of the manufacturingprocedure is described with reference to plan diagrams andcross-sectional diagrams. The following description is about amanufacturing procedure for one thermoelectric transducer 15 but theactual manufacture fabricates a number of horizontally and verticallyarrayed structures together and separates the structures in a laterstep. The thin-film process and the separation can be performed in adifferent order from the one described in the following.

FIGS. 10A and 10B are a plan diagram and a cross-sectional diagram ofthe structure after the first step. The cross-sectional diagram of FIG.10B illustrates the cross-section along the section line B-B in FIG.10A. This step applies a polyimide film 302 onto a glass substrate 301and cures it. In another example, a polyimide film 302 can be bonded toa glass substrate 301.

FIGS. 11A and 11B are a plan diagram and a cross-sectional diagram ofthe structure after the next step. The cross-sectional diagram of FIG.11B illustrates the cross-section along the section line B-B in FIG.11A. This step deposits a thermoelectric film 303 on the polyimide film302. For the thermoelectric film 303, an IGZO film can be deposited bysputtering. A different film formation method and/or a differentmaterial can be selected.

FIGS. 12A, 12B, and 12C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step removes a partof the thermoelectric film 303 to form a thermoelectric film 103. Thecross-sectional diagram of FIG. 12B illustrates the cross-section alongthe section line B-B in FIG. 12A, which is a cross-section of the areawhere the thermoelectric film is removed. The cross-sectional diagram ofFIG. 12C illustrates the cross-section along the section line C-C inFIG. 12A, which is a cross-section of the area where the thermoelectricfilm 103 exists. The thermoelectric film can be processed byphotolithography and etching. In another example, a metal mask is usedto deposit the thermoelectric film 303, which corresponds tosimultaneously depositing and patterning a thermoelectric film 103having a desired shape.

FIGS. 13A, 13B, and 13C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces afirst electrode 111. The cross-sectional diagram of FIG. 13B illustratesthe cross-section along the section line B-B in FIG. 13A, which is across-section of the area where a connection terminal part 131 isformed. The cross-sectional diagram of FIG. 13C illustrates thecross-section along the section line C-C in FIG. 13A, which is across-section of the area where an electromotive part 201 is formed. Thefirst electrode 111 can be produced by sputtering or vacuum vapordeposition with a metal mask or by photolithography and etchingfollowing full film formation on a side of the substrate.

FIGS. 14A, 14B, and 14C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces asecond electrode 112. The cross-sectional diagram of FIG. 14Billustrates the cross-section along the section line B-B in FIG. 14A,which is a cross-section of the area where a connection terminal part132 is formed. The cross-sectional diagram of FIG. 14C illustrates thecross-section along the section line C-C in FIG. 14A, which is across-section of the area where an electromotive part 202 is formed. Thesecond electrode 112 can be produced by the same method as the firstelectrode 111. Either the first electrode 111 or the second electrode112 can be produced first.

After the steps described with reference to FIGS. 10A to 14C, individualthermoelectric transducers 15 are cut out, lead wires are connected tothe connection terminals 131 and 132, and the glass substrate 301 isremoved. The order of these steps can be selected desirably. The leadwires 141 and 142 can be soldered to the connection terminal parts 131and 132 after pre-tinning the connection terminals 131 and 132 byultrasonic soldering and pre-tinning the lead wires 141 and 142. Adifferent soldering procedure can be employed.

As described above, the first electrode 111 and the second electrode 112need to be made of materials having different work functions. Sinceeffective acquisition of a thermal electromotive force is prioritizedfirst, the soldering material could have poor adhesion to the materialof the first electrode and/or the second electrode. To address thisissue, a not-shown thin film of a metal having good solderability, suchas copper, gold, or tin, can be laid on the connection terminal parts131 and 132 of the first electrode 111 and the second electrode 112.

The lead wire can be not only an electrical wire but also flexibleprinted circuits (FPC). The FPC can be connected to a connectionterminal by pre-tinning the both sides to be joined, putting the FPC onthe connection terminal part, and joining them by thermocompressionbonding. The polyimide film can be removed from the glass substrate bylaser lift-off (LLO), which irradiates the rear surface of the glasssubstrate with a laser beam to detach the polyimide film by the effectof light or heat. The soldering method of the lead wire to theconnection terminal part and the method of removing the polyimide filmfrom the glass substrate can be selected desirably.

Embodiment 2

Embodiment 1 provides a structure such that a plurality of electrodesare disposed on the same side of a thermoelectric film. This structureallows the layers of the thermoelectric film and the electrodes to bereplaced with each other. FIGS. 15 and 16 illustrate a configurationexample of a thermoelectric transducer 15 including a thermoelectricfilm and electrodes layered in a different order from those inEmbodiment 1. FIG. 16 is a cross-sectional diagram along the sectionline XVI-XVI in FIG. 15. This configuration is the same as theconfiguration in Embodiment 1 except that the order of layers of thethermoelectric film and the electrodes is different.

As illustrated in FIGS. 15 and 16, the thermoelectric film 351 is laidabove the electromotive parts 201 and 202 of the first electrode 111 andthe second electrode 112 to cover them. The outer edge of thethermoelectric film 351 is located inner than the outer edge of thesubstrate 100. The connection terminal parts 131 and 132 are disposedoutside the region of the thermoelectric film 351 and exposed.

Hereinafter, an example of the manufacturing procedure is described withreference to plan diagrams and cross-sectional diagrams. The followingdescription is about a manufacturing procedure for one thermoelectrictransducer 15 but the actual manufacture fabricates a number ofhorizontally and vertically arrayed structures together and separatesthe structures in a later step. The thin-film process and the separationcan be performed in a different order from the one described in thefollowing.

FIGS. 17A and 17B are a plan diagram and a cross-sectional diagram ofthe structure after the first step. The cross-sectional diagram of FIG.17B illustrates the cross-section along the section line B-B in FIG.17A. This step deposits a polyimide film 302 on a glass substrate 301,like in Embodiment 1.

FIGS. 18A, 18B, and 18C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces afirst electrode 111. The cross-sectional diagram of FIG. 18B illustratesthe cross-section along the section line B-B in FIG. 18A, which is across-section of the area where a connection terminal part 131 isformed. The cross-sectional diagram of FIG. 18C illustrates thecross-section along the section line C-C in FIG. 18A, which is across-section of the area where an electromotive part 201 is formed. Thefirst electrode 111 can be produced by etching, or patterning byphotolithography.

FIGS. 19A, 19B, and 19C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces asecond electrode 112. The cross-sectional diagram of FIG. 19Billustrates the cross-section along the section line B-B in FIG. 19A,which is a cross-section of the area where a connection terminal part132 is formed. The cross-sectional diagram of FIG. 19C illustrates thecross-section along the section line C-C in FIG. 19A, which is across-section of the area where an electromotive part 202 is formed. Thesecond electrode 112 can be produced by the same method as the firstelectrode 111.

FIGS. 20A, 20B, and 20C are a plan diagram and cross-sectional diagramsof the structure after the next step. The cross-sectional diagram ofFIG. 20B illustrates the cross-section along the section line B-B inFIG. 20A and the cross-sectional diagram of FIG. 20C illustrates thecross-section along the section line C-C in FIG. 20A. This step forms athermoelectric film 351 to cover the electromotive parts 201 and 202 ofthe first and the second electrodes but expose the connection terminalparts 131 and 132. For the thermoelectric film 351, an IGZO film can bedeposited by sputtering with a metal mask. A different film formationmethod and/or a different material can be selected.

A structure having a thermoelectric film on the entire side does notallow a proper signal to be taken out because the thermoelectric film isinterposed between a lead wire and a connection terminal part. Thestructure in this embodiment is configured so that the connectionterminal parts are located outside the region of the thermoelectric filmthereabove and exposed and accordingly, the lead wires and theconnection terminal parts are connected so that they can directlycontact each other. Moreover, the structure in this embodiment preventsgeneration of a parasitic device and effects of an attached object to bemeasured, like the structure of Embodiment 1.

In Embodiment 1, the two electrodes 111 and 112 have to be etchedselectively on the thermoelectric film 103 and therefore, patterningwith a metal mask is more convenient. In Embodiment 2, etching the twoelectrodes 111 and 112 is performed before forming the thermoelectricfilm 351 and therefore, the difficulty in ensuring the selectivity foretching is lowered. Etching achieves finer and more accurate patterningthan patterning with a metal mask. Accordingly, manufacturing ahigh-spec device becomes available.

Embodiment 3

FIG. 21 illustrates another configuration example of the thermoelectrictransducer 15. In comparison with the configuration of Embodiment 1, theconnection terminal parts 131 and 132 are laid on a thermoelectric film361 that contributes to generation of thermal electromotive force andthe connection terminal parts 131 and 132 are located inner than theouter edge of the thermoelectric film 361. The outer edge of thethermoelectric film 361 is located inner than the outer edge of theflexible substrate 100.

The choices for the method to join a lead wire and a connection terminalpart increase depending on the condition of use. For example, for thecondition that does not require high heat tolerance, joining withconductive adhesive can be a choice. The conductive adhesive does notdiffuse too far to penetrate the metal of an electrode or require hardcompression. Accordingly, neither the conductive adhesive as joiningmaterial nor the lead wire will contact the thermoelectric film andtherefore, the thermoelectric film provided under the connectionterminal part does not cause a problem. The thermoelectric film 361 thatcontributes to the device operation (such as sensing or electricgeneration) is processed so that its outer edge will be located innerthan the outer edge of the substrate 100. The manufacturing procedurecan be the same as the one in Embodiment 1.

In the configurations described in Embodiments 1 to 3, a rigid(non-flexible) substrate such as a glass substrate can be employed inplace of the flexible substrate.

Embodiment 4

FIG. 22 illustrates another configuration example of the thermoelectrictransducer 15. In comparison with the configuration of Embodiment 1, thethermoelectric transducer 15 in FIG. 22 includes a rigid substrate 110,instead of a flexible substrate. The substrate 110 can be a glasssubstrate.

The thermoelectric film 371 extends to ends of the substrate 110.Specifically, a part of the outer edge of the thermoelectric film 371coincides with a part of the outer edge of the substrate 110. In theexample of FIG. 22, three sides of the rectangular thermoelectric film371 coincide with three sides of the substrate 110. One side is locatedinner than the outer edge of the substrate 110. The remainingconfiguration is substantially the same as the configuration inEmbodiment 1. For example, the electrodes 111 and 112 are on a layerupper than the thermoelectric film 371 and the connection terminal parts131 and 132 of the electrodes are disposed in an unseparated areaoutside the region of the thermoelectric film 371. The connectionterminal parts 131 and 132 are distant from the thermoelectric film 371when viewed planarly. The order of layers of the thermoelectric film andthe electrodes can be reversed.

For the condition of use that does not need a flexible substrate butallows or needs a rigid substrate, the substrate used in themanufacturing process such as a glass substrate can be used as asubstrate for the thermoelectric transducer, instead of a polyimidesubstrate. In that case, the steps of forming and detaching a polyimidefilm can be excluded. The thermoelectric transducer 15 in thisembodiment can include a protection film covering the components on thesubstrate 110. In this case, the connection terminal parts are exposed.

In an example where a glass substrate is employed, the substrate has athickness of at least 0.5 mm; the thermoelectric film 371 does not droopover the cut surface. Accordingly, even if the thermoelectric film 371extends to the outer edge of the substrate 110, an object can maintain adistance from the thermoelectric film 371 and does not affect the outputof the thermoelectric transducer 15. Since the thermoelectric film doesnot exist around the connection terminal parts 131 and 132, no parasiticdevice is generated even if solder penetrates the connection terminalpart 131 or 132 or a solder joint is dislocated from the connectionterminal part 131 or 132, so that the thermoelectric transducer 15exhibits stable characteristics. If technically possible, a substratethinner than this example can be employed.

Hereinafter, an example of the method of manufacturing thethermoelectric transducer in this embodiment is described. An example ofthe manufacturing procedure does not form a polyimide film but depositsthe other components of thermoelectric transducers on a glass substrateand cuts out individual thermoelectric transducers 15. In the following,such an example of the manufacturing procedure is described withreference to plan diagrams and cross-sectional diagrams. The followingdescription is about a manufacturing procedure for one thermoelectrictransducer 15 but the actual manufacture fabricates a number ofhorizontally and vertically arrayed structures together and separatesthe structures in a later step. The thin-film process and the separationcan be performed in a different order from the one described in thefollowing.

FIGS. 23A and 23B are a plan diagram and a cross-sectional diagram ofthe structure after the first step. The cross-sectional diagram of FIG.23B illustrates the cross-section along the section line B-B in FIG.23A. This step deposits a thermoelectric film 371 having a desired shapeby sputtering with a metal mask. The thermoelectric film 371 is providedin the region other than the rectangular unseparated region where theconnection terminal parts 131 and 132 of the electrodes are to bedisposed.

Precise positioning of the metal mask is required in only one directionalong the vertical axis in FIG. 23A. Compared to the metal masks for theelectrodes 111 and 112, high precision is not necessary; thethermoelectric film 371 can be prepared by rough metal-masking. Thethermoelectric film 371 can be formed by a different method that doesnot use a metal mask.

FIGS. 24A and 24B are a plan diagram and a cross-sectional diagram ofthe structure after the next step. This step produces a first electrode111. The cross-sectional diagram of FIG. 24B illustrates thecross-section along the section line B-B in FIG. 24A, which is across-section of the area where an electromotive part 201 is formed. Thefirst electrode 111 can be produced by the same method as the one inEmbodiment 1.

FIGS. 25A and 25B are a plan diagram and a cross-sectional diagram ofthe structure after the next step. This step produces a second electrode112. The cross-sectional diagram of FIG. 25B illustrates thecross-section along the section line B-B in FIG. 25A, which is across-section of the area where an electromotive part 202 is formed. Thesecond electrode 112 can be produced by the same method as the firstelectrode 111.

Embodiment 5

FIGS. 26A, 26B, and 26C illustrate another configuration example of thethermoelectric transducer 15. FIG. 26A is a plan diagram of athermoelectric transducer 15. FIG. 26B is a cross-sectional diagram ofthe thermoelectric transducer 15 along the section line B-B in FIG. 26Aand FIG. 26C is a cross-sectional diagram of the thermoelectrictransducer 15 along the section line C-C in FIG. 26A.

In comparison with the configuration in Embodiment 1, the thermoelectrictransducer 15 in this embodiment includes a rigid substrate 110, insteadof a flexible substrate. The substrate 110 can be a glass substrate. Thethermoelectric film 381 extends to the ends of the substrate 110.Specifically, the outer edge of the thermoelectric film 381 coincideswith the outer edge of the substrate 110. In the example of FIG. 26A,the four sides of the rectangular thermoelectric film 381 coincide withthe four sides of the substrate 110. The thermoelectric transducer 15 inthis embodiment can include a protection film covering the components onthe substrate 110. In this case, the connection terminal parts areexposed.

Like the substrate in Embodiment 4, the glass substrate has a thicknessof at least 0.5 mm; the thermoelectric film 381 does not droop over thecut surface. Accordingly, even if the thermoelectric film 381 extends tothe outer edge of the substrate 110, an object can maintain a distancefrom the thermoelectric film 381 and does not affect the output of thethermoelectric transducer 15. If technically possible, a substratethinner than this example can be employed.

The thermoelectric film 381 has two openings 383 and 385. The connectionterminal parts 131 and 132 of the electrodes are disposed to be distantfrom the thermoelectric film 381 when viewed planarly, so as not tocontact with the thermoelectric film 381. That is to say, the connectionterminal parts 131 and 132 are disposed outside the region of thethermoelectric film 381. More specifically, the connection terminal part131 is disposed within the opening 383 and the connection terminal part131 is disposed within the opening 385. The electrodes 111 and 112 areon a layer upper than the thermoelectric film 385; neither theconnection terminal part 131 nor 132 are in contact with thethermoelectric film 381. The order of layers of the thermoelectric filmand the electrodes can be reversed.

Hereinafter, an example of the method of manufacturing thethermoelectric transducer in this embodiment is described. In thefollowing, an example of a manufacturing procedure including a lift-offprocess is described with reference to plan diagrams and cross-sectionaldiagrams. The following description is about a manufacturing procedurefor one thermoelectric transducer 15 but the actual manufacturefabricates a number of horizontally and vertically arrayed structurestogether and separates the structures in a later step. The thin-filmprocess and the separation can be performed in a different order fromthe one described in the following.

FIGS. 27A and 27B are a plan diagram and a cross-sectional diagram ofthe structure after the first step. The cross-sectional diagram of FIG.27B illustrates the cross-section along the section line B-B in FIG.27A. This step forms photoresist films 403 and 405 on a glass substrate110 by photolithography. As will be described later, the regions of thephotoresist films 403 and 405 correspond to the openings 383 and 385.

FIGS. 28A and 28B are a plan diagram and a cross-sectional diagram ofthe structure after the next step. The cross-sectional diagram of FIG.28B illustrates the cross-section along the section line B-B in FIG.28A. This step deposits a thermoelectric film 401 on an entire side ofthe glass substrate 110 with photoresist films 403 and 405 bysputtering, for example. The thermoelectric film 401 is laid above andin contact with the exposed surface of the glass substrate 110 and thephotoresist films 403 and 405.

FIGS. 29A, 29B, and 29C are a plan diagram and cross-sectional diagramsof the structure after the next step. The cross-sectional diagram ofFIG. 29B illustrates the cross-section along the section line B-B inFIG. 29A and the cross-sectional diagram of FIG. 29C illustrates thecross-section along the section line C-C in FIG. 29A. This step removesthe photoresist films 403 and 405 to remove the thermoelectric film inthe corresponding regions, so that a thermoelectric film 381 havingopenings 383 and 385 is obtained. The lift-off progresses from theperiphery of the pattern and therefore, a smaller area can be processedin a shorter time than a larger area. Compared to Embodiment 4, theprocess is completed in a short time because this embodiment removesonly the parts corresponding to the connection terminals.

FIGS. 30A, 30B, and 30C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces afirst electrode 111. The cross-sectional diagram of FIG. 30B illustratesthe cross-section along the section line B-B in FIG. 30A, which is across-section of the area where a connection terminal part 131 isformed. The cross-sectional diagram of FIG. 30C illustrates thecross-section along the section line C-C in FIG. 30A, which is across-section of the area where an electromotive part 201 is formed. Theconnection terminal part 131 is located inside the opening 383. Thefirst electrode 111 can be produced by the same method as the one inEmbodiment 1.

FIGS. 31A, 31B, and 31C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces asecond electrode 112. The cross-sectional diagram of FIG. 31Billustrates the cross-section along the section line B-B in FIG. 31A,which is a cross-section of the area where a connection terminal part132 is formed. The cross-sectional diagram of FIG. 31C illustrates thecross-section along the section line C-C in FIG. 31A, which is across-section of the area where an electromotive part 202 is formed. Theconnection terminal part 132 is inside the opening 385. The secondelectrode 112 can be produced by the same method as the first electrode111.

FIG. 32 illustrates a configuration example of a joint in theconfiguration example illustrated in FIGS. 31A to 31C. The connectionterminal parts 131 and 132 are not laid on the thermoelectric film 381and therefore, even if the solder joint 121 or 122 penetrates theconnection terminal parts 131 or 132, a parasitic device is notgenerated and the thermoelectric transducer 15 exhibits stablecharacteristics.

FIG. 33 illustrates another configuration example of a joint in thisembodiment. The connection terminal parts 181 and 182 in theconfiguration example in FIG. 33 are partially laid above and in contactwith the thermoelectric film 381. Specifically, the peripheral parts ofthe connection terminal parts 181 and 182 are in contact with thethermoelectric film 381. However, the solder joint 121 interconnectingthe lead wire 141 and the connection terminal part 181 and the solderjoint 122 interconnecting the lead wire 142 and the connection terminalpart 182 are located within the openings 383 and 385, respectively; theyare distant from the thermoelectric film 381 within the plane of thesubstrate. This configuration can also prevent generation of a parasiticdevice between the thermoelectric film 381 and a lead wire or a solderjoint.

Embodiment 6

FIGS. 34A, 34B, and 34C illustrate another configuration example of thethermoelectric transducer 15. FIG. 34A is a plan diagram of athermoelectric transducer 15. FIG. 34B is a cross-sectional diagram ofthe thermoelectric transducer 15 along the section line B-B in FIG. 34Aand FIG. 34C is a cross-sectional diagram of the thermoelectrictransducer 15 along the section line C-C in FIG. 34A. In comparison withthe configuration in Embodiment 5, this configuration example includesisland-like thermoelectric films 413 and 415, in addition to thethermoelectric film 411. The thermoelectric transducer 15 in thisembodiment can include a protection film covering the components on thesubstrate 110. In this case, the connection terminal parts are exposed.

The thermoelectric film 411 has the same shape as the thermoelectricfilm 381 in Embodiment 5. Specifically, the thermoelectric film 411extends to the ends of the substrate 110. The outer edge of thethermoelectric film 411 coincides with the outer edge of the substrate110. In the example of FIG. 34A, the four sides of the rectangularthermoelectric film 411 coincide with the four sides of the substrate110.

The thermoelectric films 411, 413, and 415 are separate from oneanother. As will be described later, these films are included in thesame layer of thermoelectric material produced simultaneously by thesame process. As to the shape, the thermoelectric film 411 has twoopenings like the thermoelectric film 381 in Embodiment 5; thethermoelectric films 413 and 415 are disposed within these openings. Agroove 387 is provided between the thermoelectric film 411 and thethermoelectric film 413 and a groove 389 is provided between thethermoelectric film 411 and the thermoelectric film 415. Unlike thethermoelectric film 411, neither the thermoelectric film 413 nor 415contributes to generation of thermal electromotive force (deviceoperation).

The connection terminal parts 131 and 132 are laid above and in contactwith the thermoelectric films 413 and 415, respectively. The peripheriesof the connection terminal parts 131 and 132 are located inner than theperipheries of the thermoelectric films 413 and 415 and they are distantfrom the thermoelectric film 411. The configuration such that theconnection terminal parts 131 and 132 are disposed outside thethermoelectric film 411 and within the openings of the thermoelectricfilm 411 when viewed planarly is the same as the configuration ofEmbodiment 5.

Even if some metal other than the electrodes 111 and 112 contacts thethermoelectric film 413 or 415 isolated from the thermoelectric film 411that contributes to the device operation, the contact does not affectthe voltage between the electrodes. Accordingly, even if the jointbetween a connection terminal part 131 or 132 and a lead wire penetratesthe connection terminal part, a parasitic device is not generated andthe thermoelectric transducer 15 exhibits stable characteristics.

Hereinafter, an example of the method of manufacturing thethermoelectric transducer 15 in this embodiment is described. In thefollowing, an example of a manufacturing procedure using a laser toprocess a thermoelectric film is described with reference to plandiagrams and cross-sectional diagrams. The following description isabout a manufacturing procedure for one thermoelectric transducer 15 butthe actual manufacture fabricates a number of horizontally andvertically arrayed structures together and separates the structures in alater step. The thin-film process and the separation can be performed ina different order from the one described in the following.

FIGS. 35A and 35B are a plan diagram and a cross-sectional diagram ofthe structure after the first step. This step deposits a thermoelectricfilm 419 on an entire side of the glass substrate 110 by sputtering, forexample.

FIGS. 36A, 36B, and 36C are a plan diagram and cross-sectional diagramsof the structure after the next step. The cross-sectional diagram ofFIG. 36B illustrates the cross-section along the section line B-B inFIG. 36A and the cross-sectional diagram of FIG. 36C illustrates thecross-section along the section line C-C in FIG. 36A. This step removesthe thermoelectric film 419 in the parts surrounding the areas whereconnection terminal parts are to be disposed by laser beam processing.This process forms a groove 387 between the thermoelectric films 411 and413 and a groove 389 between the thermoelectric films 411 and 415.

The grooves between thermoelectric films can be formed by removing athermoelectric film in a line, not in a plane as described in Embodiment4 and 5. Accordingly, laser beam processing is suitable because it doesnot need masking but scans the thermoelectric film 419 with a spot beamalong the cut lines.

FIGS. 37A, 37B, and 37C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces afirst electrode 111. The cross-sectional diagram of FIG. 37B illustratesthe cross-section along the section line B-B in FIG. 37A, which is across-section of the area where a connection terminal part 131 isformed. The cross-sectional diagram of FIG. 37C illustrates thecross-section along the section line C-C in FIG. 37A, which is across-section of the area where an electromotive part 201 is formed. Theconnection terminal part 131 is formed on the thermoelectric film 413.The first electrode 111 can be produced by the same method as the one inEmbodiment 1.

FIGS. 38A, 38B, and 38C are a plan diagram and two cross-sectionaldiagrams of the structure after the next step. This step produces asecond electrode 112. The cross-sectional diagram of FIG. 38Billustrates the cross-section along the section line B-B in FIG. 38A,which is a cross-section of the area where a connection terminal part132 is formed. The cross-sectional diagram of FIG. 38C illustrates thecross-section along the section line C-C in FIG. 38A, which is across-section of the area where an electromotive part 202 is formed. Theconnection terminal part 132 is formed on the thermoelectric film 415.The second electrode 112 can be produced by the same method as the firstelectrode 111.

The description about the relation between the thermoelectric film and aconnection terminal part in Embodiments 4 to 6 is applicable to athermoelectric transducer on a flexible substrate in place of a glasssubstrate.

Embodiment 7

For the manufacture of a device 15 using thin-film process includingvacuum vapor deposition, sputtering, and/or photolithography, how manydevices are taken out from one substrate is an important issue from theviewpoint of cost. The thermoelectric transducer module discussed inthis description needs to have a region for performing thermoelectricconversion, lead wires for transmitting the output to an externalmeasurement equipment, a substrate for holding them, and coverings ofthe lead wires for practical use.

Among those components, the region where the component is required to bemanufactured by thin-film process is the region for performingthermoelectric conversion, or the region where a thermoelectric film andtwo electrodes are layered. The lead wires can be manufactured easily ata lower cost by a method other than the thin-film process and therefore,connecting the lead wires to complete a device is appropriate from theviewpoint of efficiency. The region to be manufactured by thin-filmprocess includes electromotive parts for performing thermoelectricconversion and connection terminal parts to be connected with externallead wires. The electromotive part and the connection terminal part ofone electrode are connected via a short lead part and these parts aremanufactured integrally.

The foregoing embodiments have described structures based on thisconcept; however, such structures could have a problem in someconditions of use. One of such conditions is that the tolerance to hightemperature is required and another one is that the device is set in anarrow space of an object. In both cases, the proximity of theconnection terminal parts to the object region is one cause. In theformer condition, the heat tolerance of the joints becomes an issue andin the latter condition, the height of the joints becomes an issue.

As to the materials of the thermoelectric conversion region produced bythin-film process, the thermoelectric film can be an oxide semiconductorfilm. IGZO has sufficient heat tolerance to the process temperature ofapproximately 300° C. to 400° C. For the metallic electrodes, Ni has amelting point at 1455° C. Ti has a melting point at 1675° C. It is saidthat polyimide for the flexible substrate has a decompositiontemperature higher than 500° C.

As understood from the above, the materials of the thermoelectricconversion region generally have sufficient heat tolerance to thetemperature range from 300° C. to 400° C. However, the structures inwhich lead wires as independent components are connected with thethermoelectric transducer include joints and therefore, the heattolerance of the joints determines the heat tolerance of the wholedevice. The solidus temperature of high-temperature solder isapproximately 220° C. and a common anisotropic conductive film (ACF) isnot expected to be used in an environment higher than a hundred andseveral ten degrees Celsius.

In view of the foregoing, this embodiment proposes a high heat-resistivedevice having long lead regions produced integrally with athermoelectric conversion region. The whole device down to a region tobe placed at temperature tolerable for an external device can beproduced integrally, within the limitation of the size of the mothersubstrate. Alternatively, the connection terminal parts are formed atends of the lead parts elongated to the region where the heat toleranceof the joints is ensured and the lead wires produced by independentprocess can be connected to the connection terminal parts.

FIG. 39 illustrates a configuration example of the thermoelectrictransducer 15 in this embodiment. In comparison with the foregoing otherembodiments, this thermoelectric transducer 15 has long lead partsbetween the connection terminal parts and the electromotive parts forperforming thermoelectric conversion.

Specifically, the first electrode 111 and the second electrode 112 havelong lead parts 501 and 502, respectively, compared to those inEmbodiment 1. Like in Embodiment 1, the connection terminal part 131,the lead part 501, and the electromotive part 201 are formed integrallyand included in a first electrode 111 of one conductive film. Insimilar, the connection terminal part 132, the lead part 502, and theelectromotive part 202 are formed integrally and included in a secondelectrode 112 of one conductive film.

As illustrated in FIG. 39, the length L2 of the lead parts 501 and 502is longer than both of the length L1 of the thermal electromotive partand the length L3 of the connection terminal parts 131 and 132. Thelength of a lead part is defined by the distance between the thermalelectromotive part and a connection terminal part at the points wherethe thermal electromotive part and the connection terminal part areclosest to each other. The lengths of the thermal electromotive part andthe connection terminal part are their largest dimensions in thedirection parallel to the length of the lead part. The two lead partscan have different lengths and the shorter lead part is longer than bothof the thermal electromotive part and the connection terminal part. Inthe example of FIG. 39, the two lead parts 501 and 502 are straight andparallel to each other, these parts can be bent.

In the configuration in FIG. 39, the thermoelectric film 103 is providedonly in the thermal electromotive part where the electromotive parts 201and 202 are laid on the thermoelectric film 103 and is not provided inthe regions corresponding to the lead parts 501 and 502 and theconnection terminal parts 131 and 132 that are formed integrally withthe electromotive parts 201 and 202. The outer edge of thethermoelectric film 103 is located inner than the outer edge of theflexible substrate 100. On the side of the flexible substrate 100 wherethe device is fabricated, a protection layer such as a polyimide layercan be provided in the region excluding the regions of the connectionterminal parts 131 and 132. The manufacturing procedure can be the sameas the one in Embodiment 1.

This configuration achieves a device (thermoelectric transducer module)thin in the region to be attached to an object and highly resistive toheat. Furthermore, the device is free from the effect of a parasiticdevice between a lead wire and the thermoelectric film to attain properoutput.

The foregoing embodiments have described interconnection by soldering asa typical example; however, in the cases of wire bonding, compressionbonding, diffusion joining, ACF, and conductive adhesive, the joint maypenetrate the thin-film electrode so that a lead wire or a connectionterminal could directly contact the thermoelectric film. Therefore, thesame configurations in the foregoing embodiments are effective tostabilize the characteristics of the device.

As set forth above, embodiments of this disclosure have been described;however, this disclosure is not limited to the foregoing embodiments.Those skilled in the art can easily modify, add, or convert each elementin the foregoing embodiments within the scope of this disclosure. A partof the configuration of one embodiment can be replaced with aconfiguration of another embodiment or a configuration of an embodimentcan be incorporated into a configuration of another embodiment.

What is claimed is:
 1. A thermoelectric transducer comprising: asubstrate; a thermoelectric film on the substrate; a first electrode onthe substrate; and a second electrode on the substrate, the secondelectrode being different from the first electrode in work function,wherein the first electrode and the second electrode are in contact witha same side of the thermoelectric film, and wherein an outer edge of thethermoelectric film is located inner than an outer edge of thesubstrate.
 2. The thermoelectric transducer according to claim 1,wherein the substrate is a flexible substrate.
 3. The thermoelectrictransducer according to claim 1, wherein the first electrode includes afirst connection terminal part; wherein the second electrode includes asecond connection terminal part; and wherein the first connectionterminal part and the second connection terminal part are distant fromthe thermoelectric film when viewed planarly.
 4. The thermoelectrictransducer according to claim 1, wherein the thermoelectric film islocated between the substrate and both of the first electrode and thesecond electrode.
 5. The thermoelectric transducer according to claim 3,wherein the first electrode and the second electrode are located betweenthe thermoelectric film and the substrate.
 6. The thermoelectrictransducer according to claim 3, wherein the substrate is a flexiblesubstrate, wherein the first electrode includes a first lead part beingdistant from the thermoelectric film when viewed planarly, between thefirst connection terminal part and the part in contact with the sameside of the thermoelectric film, and wherein the second electrodeincludes a second lead part being distant from the thermoelectric filmwhen viewed planarly, between the second connection terminal part andthe part in contact with the same side of the thermoelectric film.
 7. Athermoelectric transducer comprising: a substrate; a thermoelectric filmon the substrate; a first electrode on the substrate; and a secondelectrode on the substrate, the second electrode being different fromthe first electrode in work function, wherein the first electrode andthe second electrode are in contact with a same side of thethermoelectric film, wherein the first electrode includes a firstconnection terminal part, wherein the second electrode includes a secondconnection terminal part, and wherein the first connection terminal partand the second connection terminal part are distant from thethermoelectric film when viewed planarly.
 8. The thermoelectrictransducer according to claim 7, wherein each of the first connectionterminal part and the second connection terminal part is located in anopening of the thermoelectric film.
 9. The thermoelectric transduceraccording to claim 7, wherein the thermoelectric film is a firstthermoelectric film, wherein the thermoelectric transducer furthercomprises: a first island-like thermoelectric film located on the samelayer as the first thermoelectric film but distant from the firstthermoelectric film; and a second island-like thermoelectric filmlocated on the same layer as the first thermoelectric film but distantfrom the first thermoelectric film, wherein the first thermoelectricfilm is located between the substrate and both of the first electrodeand the second electrode, and wherein the first connection terminal partand the second connection terminal part are in contact with the firstisland-like thermoelectric film and the second island-likethermoelectric film, respectively.
 10. The thermoelectric transduceraccording to any one of claim 7, wherein an outer edge of thethermoelectric film is located inner than an outer edge of thesubstrate.
 11. The thermoelectric transducer according to any one ofclaim 8, wherein an outer edge of the thermoelectric film is locatedinner than an outer edge of the substrate.
 12. The thermoelectrictransducer according to any one of claim 9, wherein an outer edge of thethermoelectric film is located inner than an outer edge of thesubstrate.
 13. A thermoelectric transducer module comprising: asubstrate; a thermoelectric film on the substrate; a first electrode onthe substrate; a second electrode on the substrate, the second electrodebeing different from the first electrode in work function; a first leadwire interconnected with a connection terminal part of the firstelectrode; and a second lead wire interconnected with a connectionterminal part of the second electrode; wherein the first electrode andthe second electrode are in contact with a same side of thethermoelectric film, and wherein a joint between the connection terminalpart of the first electrode and the first lead wire, the first leadwire, a joint between the connection terminal part of the secondelectrode and the second lead wire, and the second lead wire are distantfrom the thermoelectric film when viewed planarly.